I think we may be headed toward a semi-monopoly, what in other places is called a "standard."
One current example is my favorite program to hate, Microsoft Word, which IMHO is an expensive, bloated anti-intuitive kludge of a program which attempts to be everything for everybody. As a result, it's buggy and sometimes unstable, and though I have been using professional computer word processors of some kind since 1975 (!) I will occasionally lose something in Word simply because I hit a sequence of keys that I can't replicate.
I can, however, send a Word program to almost anyone in the publishing business without having to worry about compatibility. And compatibility is a problem in a manuscript of any length -- even little fly-speck errors will drive a reader crazy, and compatibility problems will generate them. They also tend to be hard to find with copy-editing, just because they are so small. So...you use the standard, even if it is a kludge.
I think Adobe is going to set the standard with Lightroom -- for one thing, it is a cross-platform program by the producer of all the Creative Suite stuff, which has now added Macromedia products to the line; Lightroom (eventually) will be made to seamlessly lock into that whole suite, a perfect fit, which you will not get with other products. Aperture, because it is not cross-platform, and because it had a rather poor launch, I think will become another program like IPhoto...good for non-pro enthusiasts who don't need cross-platform and cross-system compatibility, but not much used by pros. The other options have always seemed to me to be made for data-base operators rather than for photographers.
If I'm right, and Lightroom becomes the standard, I am fully confident that Adobe will try to make it everything for everybody, and it will become a bloated, over-expensive kludge, adding features willy-nilly. For people who doubt my prediction, look how bloated Photoshop has become. Did we really need CS2? Well, I guess you did if you want to use a D200 or a 5D, because of the lack of updates for the two-year-old CS program...
Of course, all of this may be a product of the fact that I haven't had my full ration of meds today, with their wonderful calming effects...